Php 递增一个关联数组键的值

请问如何增加关联数组中特定键的值

我正在做下面的工作，但似乎不起作用。 多谢各位

$_SESSION['cart_items'] = ["a" => 1, "b" => 1];
$product_id can be a or b.
   foreach ($_SESSION['cart_items'] AS $id => $quantity){
      if ($id == $product_id){
         $_SESSION[$product_id][$quantity] +=1;

      }
    }

照办

$_SESSION['cart_items'][$product_id]++;

照办

$_SESSION['cart_items'][$product_id]++;

---

您可以测试代码：

<?php

// start the session and avoid notice
@session_start();

// if not set session for cart_items, set first
if ( ! isset($_SESSION['cart_items'])) {
    // this is session data with product details
    $_SESSION['cart_items'] = array("a" => 1, "b" => 1);
}

// assuming if product is 'a'
$product_id = $_GET['product_name'];

// check if product 'a' exist in SESSION as KEY then add +1

if (isset($_SESSION['cart_items'][$product_id])) {
    $_SESSION['cart_items'][$product_id]++;
}

// debug value of SESSION
echo '<pre>', print_r($_SESSION, true), '</pre>';


// run this code after save in file e.g. test.php?product_name=a or text.php?product_name=b
?>

---

您可以测试代码：

<?php

// start the session and avoid notice
@session_start();

// if not set session for cart_items, set first
if ( ! isset($_SESSION['cart_items'])) {
    // this is session data with product details
    $_SESSION['cart_items'] = array("a" => 1, "b" => 1);
}

// assuming if product is 'a'
$product_id = $_GET['product_name'];

// check if product 'a' exist in SESSION as KEY then add +1

if (isset($_SESSION['cart_items'][$product_id])) {
    $_SESSION['cart_items'][$product_id]++;
}

// debug value of SESSION
echo '<pre>', print_r($_SESSION, true), '</pre>';


// run this code after save in file e.g. test.php?product_name=a or text.php?product_name=b
?>

或者您也可以执行以下操作：

或者，您也可以执行以下操作：

---

$\u会话[$id]++

$\u会话[$id]++

您确定没有执行任何其他操作吗$var++递增1您确定没有执行任何其他操作吗$var++增加1